KR20210040362A - Light diffusing member, and light diffusing structure and light-emitting structure using the same - Google Patents

Abstract

When the light diffusing member of the present invention contains rare earth compound particles and a matrix resin, the thickness of the light diffusing member is T (µm), and the amount of the rare earth compound particles added to the matrix resin is C (mass%), When the product of the thickness T and the addition amount C is 200 or more and 3000 or less, and the thickness T is 2 µm or more and less than 50 µm, the addition amount C is 10 mass% or more and 600 mass% or less, and when the thickness T is 50 µm or more and 3000 µm or less, the addition amount C Is 0.1% by mass or more and 60% by mass or less. Further, the present invention also provides a light diffusion structure in which the light diffusion member is disposed on a substrate. Further, the present invention also provides a light-emitting structure comprising the light diffusing member and the light-emitting device.

Description

Light diffusing member, and light diffusing structure and light-emitting structure using the same

The present invention relates to a light diffusing member, and a light diffusing structure and a light-emitting structure using the same.

The light-diffusing member containing light-diffusing particles in a transparent resin includes a backlight module for a liquid crystal display device used in a television or a smartphone, a screen for an image display device such as a projection television, a transparent screen used for a head-up display, a cover, or the like. It is used in various optical devices such as lighting equipment used as a sealing material or the like. Such a light diffusing member is required to have a characteristic excellent in light diffusivity while securing light transmittance. As a material expressing these properties, for example, Patent Document 1 discloses agglomerated particles of rare earth phosphate.

International Publication No. 2018/025800 pamphlet

However, the light diffusing member using the rare earth phosphate particles described in Patent Literature 1 considers the balance of light transmittance and light diffusivity, but parallel transmitted light such as a lighting fixture using a light emitting diode (LED) light source is strong in a point shape. When the light diffusing member is used for the purpose to be observed, nonuniformity of light emission such as hot spots is liable to occur, and there is room for improvement.

Accordingly, an object of the present invention is to provide a light diffusing member having light transmittance and less uneven luminescence such as hot spots.

The present invention is a light diffusion member comprising rare earth compound particles and a matrix resin,

When the thickness of the light diffusing member is T (µm) and the amount of the particles added to the matrix resin is C (mass%),

The product of the thickness T and the added amount C is 200 or more and 3000 or less,

When the thickness T is 2 µm or more and less than 50 µm, the amount C added is 10% by mass or more and 600% by mass or less,

When the thickness T is 50 µm or more and 3000 µm or less, the added amount C is to provide a light diffusing member having 0.1 mass% or more and 60 mass% or less.

Further, the present invention is to provide a light diffusion structure in which the light diffusion member is disposed on a substrate.

Further, the present invention is to provide a light-emitting structure comprising the light diffusing member and the light-emitting device.

1 is a schematic diagram showing an embodiment of a light diffusion structure of the present invention.
2 is a schematic diagram showing an embodiment of the light emitting structure of the present invention.

Hereinafter, the present invention will be described based on its preferred embodiment. The light diffusing member of the present invention contains rare earth compound particles and a matrix resin.

The rare earth compound particles are disposed inside the light diffusing member and used to generate light diffusion. Specifically, the rare earth compound particles are disposed in a state dispersed in a matrix resin, and are used to diffuse the light incident on the light diffusing member. There are generally forward diffusion and backward diffusion for the diffusion of incident light. Regarding diffusing light, the rare earth compound particles are used for either or both of forward diffusion and backward diffusion. In the following description, simply "diffusion" includes both forward diffusion and backward diffusion. In addition, in the following description, when it says "light", it means that it is light including the wavelength range of visible light.

Rare earth compounds are generally materials having a high refractive index. Due to such a point, when the rare earth compound particles are dispersed in the matrix resin and disposed, diffusion of light becomes suitable.

The rare earth compound particles used in the present invention include particles containing rare earth phosphate, rare earth silicate, rare earth oxide, and the like. The rare earth phosphate is a rare earth element represented by Ln and a general formula of Ln(PO ₃ ) ₃ or LnPO ₄ . The rare earth silicate is a rare earth element represented by Ln and a general formula of Ln ₁₀ Si ₆ O ₂₇ . The rare earth oxide is a rare earth element represented by Ln and a general formula of Ln ₂ O ₃ . Among these, the use of rare earth phosphate particles as the rare earth compound particles is preferable from the viewpoint of enhancing light diffusibility, and in particular, when the general formula LnPO ₄ is used as the rare earth phosphate, it is easy to achieve both light transmittance and light diffusivity. It is more preferable from a viewpoint.

In addition, rare-earth compounds such as rare-earth phosphates are generally materials having a high Abbe number, and have a small wavelength dependence of the refractive index compared to other high-Abe-number materials such as zirconia. That is, when light having multiple wavelengths is incident, the degree of refraction is small. As a result, diffused light with little color unevenness can be obtained by using the rare earth compound particles.

The rare earth compound is an aggregate particle formed by agglomerating a plurality of primary particles comprising a rare earth compound represented by the above-described general formula. In each of the above general formulas, Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. It is preferable if it is a thing, and it is more preferable if it shows at least 1 type of element selected from Y, La, Eu, Gd, Dy, Yb, and Lu. These rare earth compounds can be used alone or in combination of two or more.

The above-described primary particles may be polycrystals or single crystals of rare earth compounds. The aggregation of the primary particles occurs due to, for example, intermolecular force, chemical bonding, or bonding by a binder, and the aggregated particles are composed of two or more primary particles agglomerated. Such agglomerated particles can be suitably produced, for example, by a method described later.

The rare earth compound may be crystalline or amorphous (amorphous). When the rare earth compound is crystalline, it is preferable from the viewpoint of increasing the refractive index. As a rare-earth compound, when rare-earth phosphate particles are produced by, for example, a method described later, a crystalline rare-earth phosphate is obtained.

_{The rare earth compound particles preferably have a volume cumulative particle diameter D 50} of 0.1 µm or more and 5 µm or less, more preferably 0.2 µm or more and 2 µm or less, in a cumulative volume of 50 vol% by a laser diffraction scattering particle size distribution measurement method. By setting D ₅₀ in the above-described range, it is possible to obtain a high-luminance light diffusing member having further improved light transmittance and haze while preventing uneven luminescence such as hot spots. Particles having such a particle diameter can be suitably manufactured, for example, by a method described later.

The volume cumulative particle diameter D ₅₀ is measured by the following method. The rare earth compound particles are mixed with water, and dispersion treatment by ultrasonic waves is performed for 1 minute using a general ultrasonic bath. The cumulative volume particle diameter D ₅₀ can be measured using an LS13 320 manufactured by Beckman Coulter as a measuring device.

The rare earth compound particles preferably have a BET specific surface area of 1 m 2 /g or more and 50 m 2 /g or less, and more preferably 1 m 2 /g or more and 30 m 2 /g or less. The measurement of the BET specific surface area can be measured by, for example, a BET single point method using "Flowsorb 2300" manufactured by Shimadzu Corporation. For example, the amount of the measurement sample is 0.3 g, a mixed gas of nitrogen and helium is used as the adsorption gas, and the preliminary degassing condition is under atmospheric pressure and at 120°C for 10 minutes.

The light diffusing member of the present invention is constituted by including rare earth compound particles and a matrix resin. The shape of the light diffusing member is not particularly limited, and a molded body such as a sheet, film, film, or plate, or a fluid or pellet (master batch) such as a dispersion (coating liquid), ink, or paste is formed to obtain the above-described molded body. Although these can be mentioned, the form of a sheet is advantageous in that it can be easily applied to a structure including a light diffusing member. The light diffusing member may be used alone or in combination with other members such as a light source such as a light-emitting diode (LED), and may be used as a molded article for a sealing material in an LED light source.

There is no particular limitation on the type of the matrix resin included in the light diffusing member, and a resin that can be molded into a desired shape may be used, and for example, a thermoplastic resin, a thermosetting resin, an ionizing radiation curable resin, and a two-liquid mixed curable resin may be used. . Among these resins, it is preferable to use a thermoplastic resin as the matrix resin from the viewpoint of easy molding and processing into a sheet having a thickness. In addition, from the viewpoint of easy molding and processing into a thin sheet, it is preferable to use at least one or more of a thermosetting resin, an ionizing radiation curable resin, and a two-liquid mixed curable resin as the matrix resin.

Examples of thermoplastic resins include polyolefin resins such as polyethylene or polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, polyacrylic acid or esters thereof, polymethacrylic acid or esters thereof. Polyacrylic acid resins such as, polyvinyl resins such as polystyrene and polyvinyl chloride, cellulose resins such as triacetylcellulose, and urethane resins such as polyurethane.

Moreover, as an example of a thermosetting resin, a phenol resin, an epoxy resin, a melamine resin, a urea resin, an unsaturated polyester resin, an alkyd resin, a polyurethane resin, a polyimide resin, etc. are mentioned. Examples of the ionizing radiation curable resin include acrylic resins, urethane resins, vinyl ester resins, and polyester alkyd resins. As for these resins, not only polymers, but also oligomers and monomers can be used. As an example of a two-liquid mixed curable resin, an epoxy resin is mentioned.

The light diffusing member of the present invention has a light transmittance and a high haze, from the viewpoint of preventing uneven luminescence such as hot spots, the thickness T (µm) of the light diffusing member and the addition amount C of the rare earth compound particles to the matrix resin. It is preferable that (mass %) is a specific range. That is, it is preferable that the product of the thickness T and the addition amount C (hereinafter, also referred to as T×C) is 200 or more and 3000 or less.

Particularly, when the product (T×C) of the thickness T and the addition amount C is in the range of 200 or more and 3000 or less, and the thickness T is 2 µm or more and less than 50 µm, the addition amount C is preferably 10% by mass or more and 600% by mass or less. Or, when thickness T is 50 micrometers or more and 3000 micrometers or less, it is preferable that addition amount C is 0.1 mass% or more and 60 mass% or less. In any case, it is possible to ensure high haze while providing light transmittance, and as a result, it is possible to suitably prevent nonuniformity of light emission such as hot spots.

When the light diffusing member has the shape of a sheet, film, film or plate, the thickness T is preferably 2 µm or more and 3000 µm or less. When the thickness T of the light diffusing member is in this range, it has both light transmittance, haze, and ease of handling. In the case of a light diffusing structure composed of a light diffusing member disposed on a substrate to be described later, it refers to the thickness of the light diffusing member disposed on the substrate. In addition, the thickness of the light diffusing member in the light emitting structure described later refers to the shortest length along the optical axis direction of the light emitting device. Therefore, even for members of the same shape, the thickness of the light diffusing member may vary depending on the arrangement position with the light emitting device.

Here, when the thickness T of the light diffusing member is 2 µm or more and less than 50 µm, the amount C of the rare earth compound particles added to the matrix resin is more preferably 100% by mass or more and 400% by mass or less. In addition, it is more preferable that the product (T×C) of the thickness T and the addition amount C is 500 or more and 3000 or less. By setting it as such a range, it is possible to ensure a high haze while providing higher light transmittance, and as a result, it is possible to effectively prevent uneven luminescence such as hot spots. Further, a typical shape of a light diffusing member having a thickness T of 5 µm or more and less than 50 µm is a film-like and sheet-like thin-film member.

On the other hand, when the thickness T of the light diffusing member is 50 µm or more and 3000 µm or less, the product of the thickness T and the added amount C (T×C) is more preferably 500 or more and 3000 or less. By setting it as such a range, even when the thickness T is thick, it is possible to ensure high haze while providing high light transmittance, and as a result, it is possible to effectively prevent nonuniformity of light emission such as hot spots. Further, a typical shape of a light diffusing member having a thickness T of 50 µm or more and 3000 µm or less is a sheet-like or plate-like thick film-like member.

The light diffusing member of the present invention may contain particles other than the rare earth compound particles. Examples of other particles include inorganic oxide particles, inorganic sulfide particles, inorganic nitride particles, inorganic carbide particles, and inorganic phosphate particles. The mixing amount of the other particles is a mixing amount with respect to the matrix resin, preferably 50% by mass or less, and more preferably 10% by mass or less.

The rare earth compound particles used in the present invention can be subjected to a lipophilic treatment such as a coupling agent treatment or an organic acid treatment on the surface of the particles from the viewpoint of improving dispersibility in the matrix resin.

As the coupling agent treatment, for example, treatment using one or two or more coupling agents such as a silane coupling agent, a zirconium coupling agent, a titanium coupling agent, and an aluminum coupling agent can be performed on the rare earth compound particles. From the viewpoint of enhancing the dispersibility of the rare earth compound particles in the matrix resin, when a silane coupling agent is used, the silane compound formed on the surface of the rare earth compound particles by the above treatment preferably further has a lipophilic group. Examples of the lipophilic group include a linear or branched unsubstituted or substituted alkyl group having 1 or more and 20 or less carbon atoms. Examples of the substituent include an amino group, a vinyl group, an epoxy group, a styryl group, a methacrylic group, an acrylic group, a ureido group, a mercapto group, a sulfide group, an isocyanate group, and the like. From the same viewpoint, the amount of the silane compound is preferably 0.01% by mass or more and 200% by mass or less, and particularly preferably 0.1% by mass or more and 100% by mass or less with respect to the mass of the rare earth compound particles.

As the organic acid treatment, for example, treatment using an organic acid such as carboxylic acid or sulfonic acid can be performed on the rare earth compound particles. From the viewpoint of improving the affinity with the matrix resin, the carboxylic acid preferably has 1 or more and 20 or less carbon atoms, and has a linear or branched unsubstituted or substituted alkyl group. Examples of such carboxylic acids include butanoic acid, pentanoic acid, hexadecanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, cis-9-octadecenoic acid, cis, cis-9,12-octadecadienoic acid, etc. can be used.

From the viewpoint of increasing the light transmittance and increasing the luminance, the total light transmittance of the light diffusing member is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. Further, the light diffusing member preferably has a haze of 50% or more, more preferably 65% or more, and even more preferably 80% or more, from the viewpoint of preventing luminance unevenness such as hot spots.

In particular, the light diffusing member preferably has a total light transmittance of 50% or more and a haze of 50% or more, more preferably a total light transmittance of 60% or more, and a haze of 65% or more, and a total light transmittance of 70% or more. Moreover, it is more preferable that the haze is 80% or more. When the light diffusing member has such physical properties, it is possible to effectively diffuse direct sunlight from a light source while exhibiting high luminance, making it difficult to generate non-uniform light emission such as a hot spot. Further, when the total light transmittance is 70% or more and the haze is 80% or more, it is particularly suitable as a light diffusing member having high light transmittance and less likely to cause uneven luminescence such as hot spots.

The light diffusing member of the present invention may be used alone, or it may be disposed on a substrate as a coat layer to obtain a light diffusing structure shown in FIG. 1. The light diffusing structure 20 shown in the drawing has a laminated structure in which the light diffusing member 10 is disposed on the base 21. This light-diffusion structure has a high haze value while maintaining the light transmittance of the substrate. The thickness of the light diffusing member in the light diffusing structure can be changed according to the intended product. In particular, if the thickness T of the light diffusing member and the amount C of the rare earth compound particles added are within the range of the above-described relational expression, the effect of the present invention is It is fully exerted.

It is preferable that the base material used for the light diffusion structure is a base material made of a material having light transmittance. Examples of the light-transmitting material include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate, polycarbonate resins, polyacrylic acid or esters thereof. B) polyacrylic acid resins such as polymethacrylic acid or esters thereof, polyvinyl resins such as polystyrene and polyvinyl chloride, and cellulose resins such as triacetylcellulose.

The thickness of the substrate is preferably 20 µm or more and 1000 µm or less from the viewpoint of durability as a light diffusing structure and workability at the time of manufacture.

The light diffusing member of the present invention can exhibit high luminance while reducing uneven luminescence such as hot spots caused by direct sunlight from a light source. The light diffusing member of the present invention is suitably used as it is or as a light diffusing structure, for example, a display, a member for lighting, a member for windows, a member for electric light, a member for a light guide plate, a screen for a projector, and an agricultural material such as a green house.

Further, the light diffusing member may be used as a light-emitting device having a light source such as a light bulb, an LED element, or a µLED element, or as a light-emitting structure having a plurality of optical devices. Among these, when an LED element, a μLED element, or the like is used as a light source, since the ratio of emitting parallel transmitted light is higher than that of other light sources, nonuniformity of light emission such as hot spots is liable to occur. In this regard, by using the light diffusing member of the present invention, in particular, as a sealing material for light sources such as LED elements and µLED elements, it is possible to exhibit high luminance while effectively preventing non-uniformity of light emission such as hot spots.

The light emitting structure 30 shown in FIG. 2 includes a plurality of light emitting devices 31 such as LED elements, and has a structure in which a light diffusing member 10 is disposed on a light emitting surface of the light emitting device 31. . Examples of the light emitting structure having such a configuration include image display devices such as displays, mobile devices such as liquid crystal TVs, personal computers, tablets, and smartphones, and lighting fixtures.

When the light-emitting structure is used as an aspect having a light diffusing member, from the viewpoint of enhancing light emission of a specific color while exhibiting high luminance, a phosphor material is further mixed with the light diffusing member in addition to the rare earth compound particles and matrix resin. It is desirable to do it. As the phosphor material, for example, YAG (yttrium aluminum garnet), TAG (tellurium aluminum garnet), sialon, sulfide-based materials, and silicate-based materials can be used alone or in combination of two or more. By adding such a material, in addition to the color development of blue from the light-emitting device, the efficiency of color development of red and green from the light-emitting device can be increased, and as a result, the contrast of light can be made high. The mixing amount of the phosphor material is preferably 1% by mass or more and 100% by mass or less, and more preferably 10% by mass or more and 60% by mass or less with respect to the matrix resin in the light diffusing member.

Next, a method of manufacturing the light diffusing member will be described. The manufacturing method of the light diffusing member is largely divided into a step of preparing particles of a rare earth compound and a step of mixing and molding the particles and a matrix resin.

First, rare earth compound particles are prepared. In the following description, a method for producing rare earth phosphate particles will be described taking the case of using a rare earth phosphate as the rare earth compound as an example. Rare-earth phosphate is a mixture of an aqueous solution containing one or two or more rare earth element sources and an aqueous solution containing a phosphate root to form a precipitate of one or two or more rare earth phosphates, and then spray-dry the precipitate. By drying, and after that, the dried product is fired to obtain rare earth phosphate particles. Instead of this, the rare earth compound particles may be commercially available as long as they satisfy the above-described physical properties.

When generating a precipitate of rare earth phosphate, it may be carried out at a water temperature near room temperature, or may be carried out by heating. In particular, it is preferable to carry out in a heated state an aqueous solution containing a rare earth element source. When heating an aqueous solution containing a rare earth element source, the heating temperature is preferably 50° C. or more and 400° C. or less, taking into account the case of wet synthesis or hydrothermal synthesis. The heating temperature of the aqueous solution containing the rare earth element source is preferably 50°C or more and 100°C or less, and more preferably 70°C or more and 95°C or less. By carrying out under such conditions, _{rare earth phosphate particles having a desired D 50} and specific surface area and high crystallinity can be obtained.

From the viewpoint of smoothly obtaining the rare earth phosphate particles, the aqueous solution containing the rare earth element source has a concentration of the rare earth element in the aqueous solution of 0.01 mol/L or more and 1.5 mol/L or less, particularly 0.01 mol/L or more and 1 mol/L. It is preferable to use L or less, particularly 0.01 mol/L or more and 0.5 mol/L or less. In this aqueous solution, it is preferable that the rare earth element is in a trivalent ion state, or a complex ion in which a ligand is coordinated with the trivalent ion. In order to prepare an aqueous solution containing a rare earth element source, for example, a rare earth oxide (for example, Ln ₂ O ₃ or the like) may be added to the nitric acid aqueous solution to dissolve it.

From the same point of view, in the aqueous solution containing a phosphate root, the total concentration of the phosphoric acid species in the aqueous solution is 0.01 mol/L or more and 3 mol/L or less, particularly 0.01 mol/L or more and 1 mol/L or less, particularly It is preferable to set it as 0.01 mol/L or more and 0.5 mol/L or less. For pH adjustment, an alkaline species may be added. As the alkali species, for example, basic compounds such as ammonia, ammonium hydrogen carbonate, ammonium carbonate, sodium hydrogen carbonate, sodium carbonate, ethylamine, propylamine, sodium hydroxide, and potassium hydroxide can be used.

It is efficient to mix the aqueous solution containing a rare earth element source and an aqueous solution containing a phosphate root so that the molar ratio of phosphate ions to rare earth element ions is 0.5 or more and 10 or less, particularly 1 or more and 10 or less, and particularly 1 or more and 5 or less. It is preferable in that a precipitated product is obtained.

When the rare earth phosphate particles are obtained as described above, they are separated into solid-liquid by a solid-liquid separation method such as filtration or decantation, and then washed with water once or a plurality of times. Water washing is preferably performed until the conductivity of the supernatant liquid becomes, for example, 2000 µS/cm or less.

The sintering of the rare earth phosphate precipitate can be performed in an oxygen-containing atmosphere such as air. The firing conditions are preferably 80°C or more and 1500°C or less, and more preferably 400°C or more and 1300°C or less. The firing time is preferably 1 hour or more and 20 hours or less, and more preferably 1 hour or more and 10 hours or less, provided that the firing temperature is within the above-described range.

Subsequently, the rare earth compound particles obtained in the above-described process, the matrix resin, and, if necessary, a phosphor material and other components are mixed and molded into a desired shape. The particle size of the rare earth compound particles used in this step may be adjusted using a pulverizing means such as a paint shaker prior to mixing with the matrix resin.

The molding performed in this step is performed, for example, by adding and kneading rare earth compound particles to the matrix resin in a molten state, followed by an inflation method, a T-die method, a calender method, or the like (hereinafter, this molding method is referred to as ``kneading molding "Sam Browne). The light diffusing member manufactured by such a method may be used as it is, or instead, a molded light diffusing member is disposed on a substrate to form a light diffusing structure, or the light diffusing member is used as a light emitting device such as an LED element. In combination, a light emitting structure can be manufactured. In any form, the effect of the present invention is sufficiently exhibited. In addition, the light diffusing member, the light diffusing structure, and the light-emitting structure may be used in combination thereof.

As another molding, a liquid mixture containing rare earth compound particles and a matrix resin may be disposed on the surface of a substrate or a light emitting device, and a light diffusing member may be directly molded on the substrate or on the light emitting device (hereinafter, this molding method is Also referred to as ``direct molding''). In this way, it is possible to manufacture a light diffusing structure in which a light diffusing member is disposed on a substrate, and a light-emitting structure including a light diffusing member on a light-emitting device such as an LED element. In this method, for example, a coating solution is prepared by mixing a rare earth compound particle, a matrix resin, and an organic solvent, and the coating solution is used in various printing methods such as screen printing, gravure printing, offset printing, and flexo method, burrs or rollers. A method of coating or spraying and drying the surface of a substrate or a light emitting device using a spray gun or the like is mentioned.

From the viewpoint of improving the manufacturing efficiency, in the case of manufacturing the light diffusing member by kneading molding, it is preferable to shape the light diffusing member so that the thickness T of the light diffusing member is 50 µm or more and 3000 µm or less. From the same viewpoint, in the case of manufacturing the light diffusing member by direct molding, it is preferable to shape the light diffusing member so that the thickness T of the light diffusing member is 2 µm or more and less than 50 µm.

As mentioned above, although the present invention has been described based on its preferred embodiment, the present invention is not limited to the above-described embodiment.

Example

Hereinafter, the present invention will be described in more detail by examples. However, the scope of the present invention is not limited to such an embodiment.

[Example 1]

A light diffusing member was manufactured using particles of yttrium phosphate as rare earth compound particles and acrylic resin as a matrix resin.

The method for producing rare earth phosphate particles made of yttrium phosphate is as follows. That is, 600 g of water was weighed into the glass container 1, 61.7 g of 60 mass% nitric acid (manufactured by Wako Junyaku Kogyo Co., Ltd. _{) and 18.8 g of Y 2} O ₃ (manufactured by Nippon Yttrium Corporation) were added, and heated to 80°C to dissolve. To the other glass container 2, 600 g of water was weighed, and 18.8 g of 85% by mass phosphoric acid was added. Next, the contents of the glass container 2 were added into the glass container 1, and aging was performed for 1 hour to obtain a precipitate. Decantation washing was performed on the obtained precipitate, and washing was performed until the conductivity of the supernatant liquid became 100 µS/cm or less. After washing, solid-liquid separation was performed by filtration under reduced pressure, and the separated solid was dried at 120°C for 5 hours in the air, and then calcined at 900°C for 3 hours in the air to obtain yttrium phosphate particles. The particles had a D ₅₀ of 1 µm and a specific surface area of 2 m 2 /g.

Subsequently, the obtained yttrium phosphate particles and an acrylic resin (manufactured by DIC, product name: A-165) were blended so that the addition amount C of the yttrium phosphate particles to the matrix resin was 100% by mass, and 2-butanone (MEK solvent) And mixed for 60 minutes with a paint shaker to prepare a coating liquid.

Next, this coating solution is applied to a PET substrate (thickness: 100 μm) using a bar coater so that the coating film thickness is 5 μm, dried at 80° C. for 5 minutes, and composed of a light diffusing member and a PET substrate. A light diffusing structure was obtained.

[Examples 2 to 4 and Comparative Examples 1 to 3]

It was produced in the same manner as in Example 1, except that the amount C of the particles added to the matrix resin and the thickness T of the light diffusing member were changed as shown in Table 1 below.

[Example 5]

After premixing the particles of yttrium phosphate obtained in Example 1 and a polycarbonate resin (manufactured by Sumica Polycarbonate, 301-22) so that the amount C of particles added to the matrix resin becomes 5% by mass, the corresponding The mixture was extrusion-molded to produce a sheet-like light diffusing member having a length of 100 mm x a width of 100 mm and a thickness T of 75 µm.

(Examples 6 to 18 and Comparative Examples 4 to 6)

It was produced in the same manner as in Example 5 except that the amount C of the particles added to the matrix resin and the thickness T of the light diffusing member were changed as shown in Table 1 below.

[Examples 19 to 27]

The yttrium phosphate particles were prepared so that the particle diameter D ₅₀ was 0.3 µm and the specific surface area was 8 m 2 /g. It was produced in the same manner as in Example 1, except that the amount C of the particles added to the matrix resin and the thickness T of the light diffusing member were changed as shown in Table 1 below.

(Examples 28 and 29)

In place of yttrium phosphate, yttrium oxide particles (made by Nippon Yttrium Co., Ltd.: D ₅₀ : 0.3 µm, specific surface area: 10 m 2 /g) were used instead of yttrium phosphate. It was produced in the same manner as in Example 1, except that the amount C of the particles added to the matrix resin and the thickness T of the light diffusing member were changed as shown in Table 1 below.

〔Light transmittance and haze〕

It measured using a haze meter (Nippon Denshoku Kogyo Co., Ltd. make, NDH2000). The light transmittance was evaluated as the total light transmittance (%). In addition, the overall evaluation of light transmittance and haze was evaluated based on the following criteria. These results are shown in Table 1 below.

〔Presence or absence of hot spots〕

AS-LC01 manufactured by Asahi Denki was used as the LED light source. The light diffusing member or light diffusing structure of Examples and Comparative Examples was disposed at a position of 1 cm above the LED light source, and the presence or absence of a hot spot was confirmed by setting the light emission of the LED light source into a high luminance mode. In the evaluation of the presence or absence of a hot spot, when the LED light source is visually confirmed through a light diffusing member or light diffusing structure, the outline (hot spot) of the LED light source is not clearly visible, and the outline is clearly defined. What was shown was set to "x". The evaluation results are shown in Table 1 below.

In addition, evaluation of light transmittance, haze, and hot spot were synthesized and evaluated according to the following criteria. The evaluation results are shown in Table 1 below.

<Comprehensive evaluation>

A: Total light transmittance is 70% or more, haze is 80% or more, and hot spots are not clearly visible.

B: The total light transmittance is 50% or more, and hot spots are not clearly visible.

C: The total light transmittance is less than 50%, or a hot spot is clearly visible.

As shown in Table 1, Examples 1 to 29 in which the thickness T of the light diffusing member, the amount C of the rare earth compound particles added to the matrix resin, and the product (T×C) thereof are in an appropriate range are Comparative Examples 1 to Compared with 6, it can be seen that it is a light diffusing member that has both light transmittance and light diffusivity, and in which hot spots are not clearly visible. Accordingly, it can be seen that the light diffusing member of the present invention, and the light diffusing structure and light-emitting structure including the light diffusing member, have both high light transmittance and high haze, and that there are few luminous irregularities such as hot spots.

Advantageous Effects of Invention According to the present invention, there are provided a light diffusing member having light transmittance and less uneven luminescence such as a hot spot, and a light diffusing structure and a light-emitting structure using the same.

Claims (9)

As a light diffusing member comprising rare earth compound particles and a matrix resin,
When the thickness of the light diffusing member is T (µm) and the amount of the particles added to the matrix resin is C (mass%),
The product of the thickness T and the added amount C is 200 or more and 3000 or less,
When the thickness T is 2 µm or more and less than 50 µm, the amount C added is 10% by mass or more and 600% by mass or less,
When the thickness T is 50 µm or more and 3000 µm or less, the amount C added is 0.1% by mass or more and 60% by mass or less. The method of claim 1,
_{The light diffusing member, wherein the particles have a volume cumulative particle diameter D 50} in a cumulative volume of 50% by volume by a laser diffraction scattering particle size distribution measurement method of 0.1 µm or more and 5 µm or less. The method according to claim 1 or 2,
A light diffusion member having a total light transmittance of 50% or more and a haze of 50% or more. The method according to any one of claims 1 to 3,
The particles are rare earth phosphate particles. The method of claim 4,
The particles are represented by Ln(PO ₃ ) ₃ or LnPO ₄ , and Ln in the formula is Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, A light diffusion member comprising at least one element selected from the group consisting of Yb and Lu. The method according to any one of claims 1 to 5,
A light diffusing member having a BET specific surface area of 1 m 2 /g or more and 50 m 2 /g or less of the particles. A light diffusing structure comprising the light diffusing member according to any one of claims 1 to 6 disposed on a substrate. A light-emitting structure comprising the light diffusing member and the light-emitting device according to any one of claims 1 to 6. The method of claim 8,
The light emitting device is a light emitting diode, a light emitting structure.

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